does CONFIG_UNUSED_SYMBOLS have any value anymore?

does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Robert P. J. Day]

  just curious -- under kernel hacking, there is the option
UNUSED_SYMBOLS to "Enable unused/obsolete exported symbols" using
EXPORT_UNUSED_SYMBOL[_GPL].  reads the help text (in part):

"This option is provided temporarily to provide a transition period in
case some external kernel module needs one of these symbols anyway."

but it's not clear if that means that it was a *one-time* transition
aid which is now unnecessary, or whether it's an *ongoing* aid which
might be used at any time.  currently, there are no invocations of
EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
this feature can be tossed?  or might it still be used every so often?

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Stefan Richter]

Robert P. J. Day wrote:
...
> it's not clear if that means that it was a *one-time* transition
> aid which is now unnecessary, or whether it's an *ongoing* aid which
> might be used at any time.  currently, there are no invocations of
> EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
> this feature can be tossed?  or might it still be used every so often?

git-blame (or qgit, which I actually used) points from this part of
lib/Kconfig.debug to the following chunk in
Documentation/feature-removal-schedule.txt:

What:	Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
	(temporary transition config option provided until then)
	The transition config option will also be removed at the same time.
When:	before 2.6.19
Why:	Unused symbols are both increasing the size of the kernel binary
	and are often a sign of "wrong API"
Who:	Arjan van de Ven <arjan@linux.intel.com>
-- 
Stefan Richter
-=====-=-=== -=== =--==
http://arcgraph.de/sr/

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Arjan van de Ven]

Stefan Richter wrote:
> Robert P. J. Day wrote:
> ...
>> it's not clear if that means that it was a *one-time* transition
>> aid which is now unnecessary, or whether it's an *ongoing* aid which
>> might be used at any time.  currently, there are no invocations of
>> EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
>> this feature can be tossed?  or might it still be used every so often?

it's one of those pieces of infrastructure that get used from time to 
time to phase out symbol exports... we should be more agressive about 
that; about 1/3rd of the exports is not used by anything in linux, yet 
each symbol costs about 100 bytes of memory at runtime.

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Robert P. J. Day]

On Thu, 19 Jul 2007, Stefan Richter wrote:

> Robert P. J. Day wrote:
> ...
> > it's not clear if that means that it was a *one-time* transition
> > aid which is now unnecessary, or whether it's an *ongoing* aid which
> > might be used at any time.  currently, there are no invocations of
> > EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
> > this feature can be tossed?  or might it still be used every so often?
>
> git-blame (or qgit, which I actually used) points from this part of
> lib/Kconfig.debug to the following chunk in
> Documentation/feature-removal-schedule.txt:
>
> What:	Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
> 	(temporary transition config option provided until then)
> 	The transition config option will also be removed at the same time.
> When:	before 2.6.19
> Why:	Unused symbols are both increasing the size of the kernel binary
> 	and are often a sign of "wrong API"
> Who:	Arjan van de Ven <arjan@linux.intel.com>

argh.  i should have checked there first.  sorry for the noise.  i can
patch that baby out unless arjan wants to do it.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Robert P. J. Day]

On Thu, 19 Jul 2007, Arjan van de Ven wrote:

> Stefan Richter wrote:
> > Robert P. J. Day wrote:
> > ...
> > > it's not clear if that means that it was a *one-time* transition
> > > aid which is now unnecessary, or whether it's an *ongoing* aid which
> > > might be used at any time.  currently, there are no invocations of
> > > EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
> > > this feature can be tossed?  or might it still be used every so often?
>
> it's one of those pieces of infrastructure that get used from time
> to time to phase out symbol exports... we should be more agressive
> about that; about 1/3rd of the exports is not used by anything in
> linux, yet each symbol costs about 100 bytes of memory at runtime.

ok, so maybe its removal file entry should be deleted if it's going to
hang around.  your call.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Arjan van de Ven]

Robert P. J. Day wrote:
> On Thu, 19 Jul 2007, Arjan van de Ven wrote:
> 
>> Stefan Richter wrote:
>>> Robert P. J. Day wrote:
>>> ...
>>>> it's not clear if that means that it was a *one-time* transition
>>>> aid which is now unnecessary, or whether it's an *ongoing* aid which
>>>> might be used at any time.  currently, there are no invocations of
>>>> EXPORT_UNUSED_SYMBOL[_GPL] anywhere in the tree.  so does that mean
>>>> this feature can be tossed?  or might it still be used every so often?
>> it's one of those pieces of infrastructure that get used from time
>> to time to phase out symbol exports... we should be more agressive
>> about that; about 1/3rd of the exports is not used by anything in
>> linux, yet each symbol costs about 100 bytes of memory at runtime.
> 
> ok, so maybe its removal file entry should be deleted if it's going to
> hang around.  your call.
> 

the removal entry is/was for the symbols *marked*, not for the 
infrastructure....

Re: does CONFIG_UNUSED_SYMBOLS have any value anymore?

[Robert P. J. Day]

On Thu, 19 Jul 2007, Arjan van de Ven wrote:

> the removal entry is/was for the symbols *marked*, not for the
> infrastructure....

ah, gotcha.  so the infrastructure itself is still useful from time to
time, then.  ok.

rday
-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================